Makefile.sub: fix dependency of RUBYDEF

* win32/Makefile.sub (RUBYDEF): fix dependency, win32/mkexports.rb
  requires rbconfig.rb.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57186 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

win32/Makefile.sub

@@ -1038,7 +1038,7 @@ $(LIBRUBY_SO):	$(LIBRUBY_A) $(DLDOBJS) $(RUBYDEF) $(RUBY_SO_NAME).res
 		$(Q) $(LDSHARED_2)
 # | findstr -v -c:LNK4049 -c:LNK4217
 
-$(RUBYDEF):	$(LIBRUBY_A) $(PREP)
+$(RUBYDEF):	$(LIBRUBY_A) $(RBCONFIG)
 		$(ECHO) generating $(@:\=/)
 		$(Q) $(MINIRUBY) $(srcdir)/win32/mkexports.rb \
 		  -output=$@ -arch=$(ARCH) $(LIBRUBY_A)